The claim: The Impossible Burger contains more estrogen than transgender hormone therapy
While only about 5% of U.S. adults consider themselves vegetarian, this hasn't stopped plant-based foods from going mainstream.
A big selling point for products like the meatless meat substitute Impossible Burger, aside from sustainability, is health. But the patty's perceived health benefits have received some criticism, including from social media users who claim the burgers contain a potent payload of hormones.
"You've probably heard of the 'Made 100% from plants'... Well, (the Impossible Burger) contains 44mg of estrogen," reads a tweet shared in an Aug. 26 Facebook post.
The tweet asserts this alleged dose is far greater than the "4 mg" of estrogen contained in hormone replacement therapy given to individuals undergoing gender reassignment.
If you eat this burger, the tweet concludes, it "will make you female."
The post and similar ones have racked up hundreds of interactions across Facebook and Instagram within the last few months, according to CrowdTangle, a social media insights tool.
Like many meat alternatives, the Impossible Burger uses soybean, or soy, as a protein source. Soy and other foods like wheat, lentils and apples contain a naturally occurring hormone called isoflavone, a type of plant estrogen (or phytoestrogen).
Isoflavone does function similarly to estrogen in mammals, but it isn't as biologically strong. And Impossible Burgers don't contain nearly enough to make anyone female.
USA TODAY reached out to the Facebook user for comment. The Twitter user did not reply to a request for comment.
Isoflavone similar to human estrogen but weaker
Estrogen, a hormone naturally produced by both males and females – animals and humans alike – can be found in trace amounts in all animal products consumed, whether it be milk, red meat or even eggs.
Its plant-derived counterpart, isoflavone, is also found in various fruits and vegetables and products derived from them, like the Impossible Burger. The meat alternative, however, doesn't contain nearly as much isoflavone as the tweet claims – under 2 mg in a single four-ounce serving, according to the company's website.
This quantity is well below that of some standard hormone treatments recommended for individuals transitioning to female, which can range up to 8 mg of estradiol (one of three forms of estrogen produced by the body) per day.
Once ingested, isoflavones bind to proteins called receptors that recognize mammalian estrogen, but the interaction is rather weak. Isoflavones also don't bind to all types of estrogen receptors found throughout the body as well as mammalian estrogen does, Kevin Klatt, a postdoctoral fellow at the Baylor College of Medicine, told fact-checking site Health Feedback.
So while isoflavones can create biological activity to some extent, they can also prevent their more potent cousin estrogen from binding to its receptors, thus simultaneously exerting anti-estrogenic effects.
Eating soy in moderation doesn't feminize men
To date, no studies have shown eating soy or isoflavones in moderation can feminize males or affect childhood development. Soy products have been a mainstay in Asian diets for centuries with no detriment to the male population, Marion Nestle, a professor of nutrition and food studies at New York University, told The Washington Post in 2019.
"Asians have been eating soy products for millennia and don't seem to be any the worse for it. They have among the longest lifespans and best health, at least in classic diets," she told the Post. "There is a special concern about ... men and boys who eat soy products, but again, if you look at populations that eat a lot of soy products, there is no evidence of particular problems."
One report often used to bolster consumer fears is a 2008 case report of a 60-year-old Texas man who developed a benign swelling of male breast tissue and elevated estrogen levels. Doctors reported the man drank three quarts of soymilk a day, which "would have given him a daily dose of 360 mg of isoflavones, about 10 times what the average man in Asia consumes‚" according to Nutrition Action, a resource website produced by the Center for Science in the Public Interest.
It's important to note, excessive intake of any food can have detrimental health consequences. For instance, eating too much salt can lead to high blood pressure, heart disease and even calcium loss from bones.
Claim made by cattle veterinarian
The claim casting suspicion on the Impossible Burger first appeared in a December 2019 article written by James Stangle, a cattle veterinarian based in South Dakota, for Tri-State Livestock News.
In the original article, Stangle asserted the 44 mg of estrogen contained in Burger King's Impossible Whopper – which uses the Impossible Foods patty – was "18 million times" greater than the "2.5 (nanograms)" in the regular beef whopper.
This colossal difference, he claimed, was "enough estrogen to grow boobs on a male."
Stangle later issued a retraction acknowledging his 18 million figure was inaccurate and that in moderation, eating an occasional Impossible Whopper would be unlikely to lead to any harm. He also acknowledged to the Atlantic in February 2020 that there was "no evidence" eating the meatless substitute could cause a man to grow breasts.
Our rating: False
Based on our research, we rate FALSE the claim the Impossible Burger contains more estrogen than transgender hormone therapy. Soy-based products, like the Impossible Burger, contain a type of estrogen called isoflavone that is similar to mammalian estrogen but is much weaker and not nearly as potent. The Impossible Burger's isoflavone content is under 2 mg, which is less than some standard dosages recommended for transgender hormone therapy. To date, there has been no evidence linking soy or isoflavone consumption with feminizing males or affecting childhood development.
Our fact-check sources:
Gallup, accessed Sept. 7, What Percentage of Americans Are Vegetarian?
Food Dive, May 27, 2020, Plant-based food sales outpace growth in other categories during pandemic
Bloomberg, Aug. 11, Plant-Based Food Sales to Increase Fivefold by 2030, BI Says
Harvard Health Publishing, Aug. 15, 2019, Impossible and Beyond: How Healthy are these meatless burgers?
NIH National Library of Medicine, accessed Sept. 9, Isoflavone
Iranian Journal of Public Health, Feb. 11, 2015, Hormones in Dairy Foods and Their Impact on Public Health - A Narrative Review Article
Impossible, Aug. 27, Soy: Facts, Myths and Why It's In Our Products
UCSF Transgender Care, June 17, 2016, Overview of feminizing hormone therapy
Hormone Health Network, accessed Sept. 9, Estradiol
Health Feedback, Jan. 10, 2020, Impossible Whopper contains no estrogen; will not lead to men growing breasts if eaten in moderation
AACE Endocrine Practice, May 1, 2008, An Unusual Case of Gynecomastia Associated with Soy Product Consumption
Nutrition Action, Jan. 7, 2015, How to Diet: Does Soy Impact Masculinity?
The Washington Post, Dec. 26, 2019, Dear men: There's no evidence that eating Impossible Whoppers will give you breasts
Cleveland Clinic, Dec. 13, 2020, Soy Foods
Nutrients, Jan. 4, 2018, Soy Consumption and the Risk of Prostate Cancer: An Updated Systematic Review and Meta-Analysis
American Heart Association News, March 23, 2020, Soy-rich foods like tofu may help lower heart disease risk
Harvard T.H. Chan School of Public Health, accessed Sept. 9, Salt and Sodium
Tri-State Livestock News, Dec. 20, 2019, Stangle: Impossible Burgers are made of what?
Tri-State Livestock News, Dec. 31, 2019, Guest Opinion by Dr. Jim Stangle, DVM: The Impossible Whopper Retraction (Sort of)
The Atlantic, Feb. 3, 2020, Why Men Think Plant-Based Meat Will Turn Them Into Women
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This article originally appeared on USA TODAY: Fact check: Eating Impossible Burgers won't feminize men